Pathways of clay mineral transport in the coastal zone of the Brazilian continental shelf from Ceará to the mouth of the Amazon River |
| |
| Authors: | J O de Morais M Tintelnot G Irion L Souza Pinheiro |
| |
| Institution: | (1) State University of Ceará, 60160110 Fortaleza, Brazil;(2) Wieblinger Weg 29/4, 69123 Heidelberg, Germany;(3) Research Institute Senckenberg, Department of Marine Research, Suedstrand 40, 26382 Wilhelmshaven, Germany |
| |
| Abstract: | The transport pathways of fine sediments (fraction <2 μm) along the Brazilian continental shelf from Ceará to the Amazon River
mouth were studied by means of clay mineral analyses. On the continental shelf southeast of the Amazon mouth, fluctuations
in clay mineral compositions reflect simple mixing between the suspended load of the North Brazil Current and sediment from
several smaller rivers. Previously, clay mineral variations west of the Amazon mouth have been explained by variable settling
velocities of different grain-size classes within the <2 μm fraction or by selective coagulation of individual clay mineral
groups. By contrast, our experiments with river bank samples show that selective coagulation does not occur in Amazon River
sediments. A more appropriate explanation for observed variations in clay mineral composition off the Amazon mouth seems to
be, similarly to that for the shelf between Ceará and the Amazon mouth, a mixing of Amazon sediments with suspended material
of the North Brazil Current. This interpretation is supported by data on clay mineral composition east and south of the Amazon
mouth, showing more affinity to sediments of the North Brazil Current than to the suspended load of the Amazon River. Additionally,
relatively low sedimentation rates and low concentrations of fine-grained sediments on the shelf suggest that high riverine
input by the Amazon River does not overprint the sediments of the North Brazil Current in this region. The strong North Brazil
Current shunts the Amazon suspended load in a north-westerly direction along the north-eastern coast of South America. Hence,
stronger sedimentation of Amazon sediments would occur only west of the river mouth. |
| |
| Keywords: | |
| 本文献已被 SpringerLink 等数据库收录！ |
|
